At present, vitrectomy apparatuses present on the market are complex, and complete in the sense that they are able to provide the surgeon with all of the functions that he may need during surgery.
Therefore, vitrectomy apparatuses are equipped with:                an irrigation system through which they allow the supply of a liquid into the back chamber of the eye;        a system for the continuous infusion of gas (sterile air) into the back chamber;        a suction circuit which can also be connected to the eye, for sucking out both liquids and gases;        and auxiliary pneumatic circuit for both controlling the operation of a second system for discontinuous infusion (pressurised air is used as a propellant for the fluid for infusion, such as a silicone oil) and for activating a first handpiece, that is to say, a device which the surgeon holds in his hand and uses for breaking up the vitreous humour. The handpiece usually comprises either micro-scissors or a blade or guillotine cutting edge, and may be either pneumatically activated (by means of the auxiliary pneumatic circuit) or electrically activated;        a lighting circuit which powers a light source (usually an optical fibre) mounted on a second handpiece which the surgeon holds in his hand and inserts in the back chamber to make the operating area visible;        a device for generating laser beams to be used for inducing a choriorentinal pexy;        a control unit for controlling all of the various functions (computer);        an interface for interaction with the control unit, normally consisting of a display and a keyboard and/or of a touch screen display;        a control pedal for most of the functions; and        a mobile instrument holder tray.        
It should be noticed that both the supply of fluids into the back chamber and their suction out can be performed, depending on requirements, either by means of suitable pipes fixed to the eyeball at sclerotomies, or by means of handpieces operated by the surgeon.
However, during vitreoretinal surgery, usually three holes are made in the eyeball, a first hole where a supply device is fixed for supplying an operating fluid (liquid or gas) into the back chamber; a second hole through which the surgeon inserts a lighting handpiece/probe; and a third hole through which the surgeon on each occasion inserts the handpiece/tool used for the actual operation, that is to say, the handpiece/tool for breaking up and sucking out the vitreous humour, the one for injecting further fluid, the one used for the choriorentinal pexy, etc. In terms of its structure, the vitrectomy apparatus usually has a main body extending mainly vertically, mounted on wheels so that it can easily be moved, and in which the various systems, circuits and the devices listed above are installed. On the front side of the main body there are many infeed/outfeed ports/connections, for the connection of various accessories intended for the various applications.
For example, each vitrectomy apparatus may comprise a plurality of irrigation outfeeds for liquids which are the same or different, a plurality of infusion outfeeds for sterile air or other gases, one or more infusion outfeeds, one or more suction inlets for liquids and/or gases, one or more infeeds for liquids or gases for infusion, one or more lighting outfeeds, one or more connections for pneumatically supplying handpieces or discontinuous infusion devices, one or more outfeeds for producing the laser beam, etc.
Each connection allows the connecting up of various probes/tools/handpieces with which the surgeon can carry out the operation. Each probe/tool/handpiece is usually connected to the relative connection on the main body of the apparatus by a flexible connecting element, guaranteeing maximum freedom of movement.
The control unit is programmed and programmable for carrying out various functions (each unit may also allow the saving of hundreds of different programs) and can both manage the various functions in a fully automatic way depending on commands received via the interface, or manage one or more functions based on commands transmitted by the surgeon using the pedal during the operation.
For example, continuous irrigation and suction may be jointly controlled automatically so as to keep the intraocular pressure substantially stable (or rather, within a predetermined range) during an entire phase of the operation.
In contrast, the discontinuous infusion circuit is usually controlled directly by the surgeon using the pedal control.
Moreover, in the event of a suction error by the surgeon (for example of the retina), the vitrectomy apparatus allows the surgeon to activate, with the pedal, a function which produces a fluid reflux through the handpiece which is normally only used for suction.
Although vitrectomy apparatuses are relatively complex, as already indicated, this invention relates exclusively to their capacity for directly supplying fluids into the back chamber (therefore, usually the irrigation and infusion of sterile liquid or air, whilst it excludes the infusion of substances by means of the pneumatic push circuit). A diagram of a system for feeding air or liquid currently widely used in vitrectomy apparatuses is illustrated in FIG. 9, which shows how the feeding system S has two outfeeds, one outfeed A for the air and one outfeed L for the liquid. Connected to the two outfeeds there are two pipes C which connect them to two infeed ports of a three-way switching valve V. The main pipe M to the supply device to be used in the eye is connected to the valve outfeed. In this case, switching between supplying air or liquid into the eye is performed by the surgeon by simply switching the valve V. This invention was devised in particular with reference to several problems which may arise during surgery involving the vitreous humour performed using vitrectomy apparatuses, although said problems are not actually caused by the vitrectomy apparatuses.
First, it has been seen that, in particular after vitrectomy operations, there may be damage to the endo-ocular circulatory system, including inhibited platelets, inhibited clotting factors, loss of electrolytes, etc.
Second, it has been found that in most vitreoretinal surgeries it is quite difficult to completely remove from the eye the substances used as endo-ocular tamponades, such as liquid perfluorocarbons, and that the related residues remaining in the eye subsequently cause inflammatory and proliferative phenomena affecting the retina and intraocular tissues. The presence of such residues may also modify the physical and rheological properties of the tamponades used post-operatively, causing potential iatrogenic damage to the intraocular structures.